Been itching to get this outta my head and onto print.........Say we never went to the 4 strokes and kept the 500`s,now with our current electronics etc would we be seeing an entirely different field coming from 250`s ? Personally I think we`d see lap times shattered by the likes of the usual aliens but we`d also maybe see the likes of Simon.Iannone,Smith,Redding and others displaying a totally different way of riding a 500 with full TC,launch control etc. Am I pipe dreaming ? Let us know what you think please.
Joined Jun 2007
10K Posts | 1K+
Norah Head
Been itching to get this outta my head and onto print.........Say we never went to the 4 strokes and kept the 500`s,now with our current electronics etc would we be seeing an entirely different field coming from 250`s ? Personally I think we`d see lap times shattered by the likes of the usual aliens but we`d also maybe see the likes of Simon.Iannone,Smith,Redding and others displaying a totally different way of riding a 500 with full TC,launch control etc. Am I pipe dreaming ? Let us know what you think please.
Two strokes were at the end of their development.
They would not need as invasive electronics as they were relatively well mannered to ride.
You can't have launch control anyway and it was mainly to help the rampant power of the 4 strokes.
I'm pretty perplexed as to why the myth of the "amazing" two strokes persists.
Many moons ago many tech people ( JB included ) went through hours of explaining that two strokes had reached the end of their development.
Where they may be of benefit would be the usual lesser weight and lack of rotational part mass rendering the bike more able to change direction.
But I very much doubt any mod.con would bring a 500 two stroke anywhere near an 800 4 stroke. They have just moved too far ahead on 4 stroke technology. Its hard I know because one always remembers the days when two strokes creamed 4 strokes ........ but that was when twp strokes were fully developed and 4 strokes not very evolved.
Edit: oh and ........ fuel economy ........ the two stroke would never make it home on the amount of gas they are allowed these days.
Joined Jun 2007
10K Posts | 1K+
Norah Head
Believe me there was no more ardent two stroke fan than me, but they have seen their day in high performance engines.
Oddly they still have a use in extremely large DI engines, but they are very low performance engines per swept volume, ie. engines where all combustion has occurred before the exhaust is opened ....... think huge ship engines.
Now theres a go ........ how about a two stoke ship engine with simillar perfornance/swept volume to an old 500
...... it would be possible to get ocean liners to plane
Oddly they still have a use in extremely large DI engines, but they are very low performance engines per swept volume, ie. engines where all combustion has occurred before the exhaust is opened ....... think huge ship engines.
Now theres a go ........ how about a two stoke ship engine with simillar perfornance/swept volume to an old 500
Joined Feb 2007
11K Posts | 2K+
Tennessee
I think its because for years, the 2 stroke would produce equal HP with half the displacement. For some fans, that makes the 2 stroke a superior engine. Even now , the Moto2 600's that have 2.5 times the displacement as the 250's, and are still running slower race times. Of course the 600's are governed to about 2/3's of their potential and weigh more, but that doesnt mean anything to the 2 smoke fan. Like you said, they had just about reached the end of development possibilities and the only place to go was more displacement.It would be interesting to see what a 750 2 smoke would do against a RC211v.
Joined Jun 2007
10K Posts | 1K+
Norah Head
Did you never ride an old 750 2 stroke? ..... they were pretty attrocious
Joined Jun 2007
10K Posts | 1K+
Norah Head
Did you never ride an old 750 2 stroke? ..... they were pretty attrocious
Allot of people believe the two stroke was at the end of it's development but that is very far from the truth.
There is something called a Direct Injection two stroke. This is an engine where the fuel is direct injected into the combustion chamber after the piston closed all the ports in the cylinder. Thus reducing the consuption and emmisions of the engine to the level of a four stroke. Combine this with an electronical controlled powervalve wich affects port timing and you have a very versatile engine wich can be tuned for torque or peak power with the push of a button. To make a long story short this kind of two stroke can behave like a modern four stroke or an old school two stroke by simply changing the mapping of the engine.
The fact of the matter is Honda was very keen to push the four stokes to MGP and to Moto2 since they are a four stroke company. And maybe 10 years ago it was a logical step. But this came with the price of traction control. I think the current engines are unridable without traction control. An 800cc four stroke engine with 230 hp is more diffucult to control and more peaky than a 500cc two stroke. When TC was banned from F1 the engines where modified aswell for the same reason. This is the main reason why electronics became so important, if you want allot of power you simply need them in order to contol it.
On the other hand if MGP would still use two strokes, the electronics would be just as important as they are now. And I don't think the field would be closer. What I know for sure is that Ducati would not be a part of it, but a company like KTM could be.
MOB
Joined Jun 2007
10K Posts | 1K+
Norah Head
No DI will do noting as it is not a performance mod. Its a way of metering out just enough fuel to burn before the exhaust port opens. I already mentioned this. Its fine if you don't really want a huge amount of power from the engine. DI is not new its pretty old really. Most ship engines are DI amd the old hot bulb engines were DI in effect.
There was a few stories a coule of years back about how some companies were going to ressurect DI and two strokes but ....... it hasn't happened. Mainly cos it was all sales hype and they failed to say just how low performance fuel efficiency tuned DI engines are.
The only attempt to actually use DI was one of the outboard engine makers ( Yamaha? ) in an attempt to maintain the use of there two stroke engine production ..... but it hasn't caught on.
One of the biggest power hikes ever gained in two strokes was the expansion chamber, DI would render chambers useless so there's a huge loss of performance immediately.
Two strokes were from the day when folk didn't care how much fuel they wasted.
These days even engine techs want the power that that wasted fuel can give.
I never claimed the DI 2-stroke would increase performance and as you said it won't.
http://www.youtube.com/watch?v=8Og0JCGKmQ4&feature=related
In this video you can clearly see there is no more fuel wasted since it's injected in a closed combustion chamber. This cannot be said of a high performance four stroke where there is something called valve overlap. This is a moment where both the inlet and outlet valves are opened at the same time. This helps the performance at high rmp but wastes fuel at low rpm just as an ordinary two stroke. This can be seen at at corner entry with the current MGP when the exhaust spits out flames. I'dont know if every bike does it but I've seen pictures where the exhaust of the M1 seems to be on fire.
I think you are confused between an injected two stroke and a direct injected two stroke. With an injected two stroke all they did was replace the carb with a low presure injection system, while the DI engine injects into the combustion chamber.
The statement that expansion chambers become useless with DI is wrong. They can still be used. The only difference is that they only force air back into the cylinder instead of air and fuel.
Is there a future for the DI engine? I don't know
Aprilia has built a 600cc DI 2-stroke but it was cancelled and the rsv mille was produced instead. Aprilia was affraid nobody was intrested in a new 2 stroke.
Ktm will change there two stroke range to DI in the near future
The fact is that the DI 2-stroke is lighter, cheaper, smaller and more efficient than it's four stoke brother, but still has a bad reputation with the general public.
http://twostrokemotocross.com/2009/06/two-strokes-strike-back/
MOB
Joined Jun 2007
10K Posts | 1K+
Norah Head
I never claimed the DI 2-stroke would increase performance and as you said it won't.
http://www.youtube.com/watch?v=8Og0JCGKmQ4&feature=related
In this video you can clearly see there is no more fuel wasted since it's injected in a closed combustion chamber. This cannot be said of a high performance four stroke where there is something called valve overlap. This is a moment where both the inlet and outlet valves are opened at the same time. This helps the performance at high rmp but wastes fuel at low rpm just as an ordinary two stroke. This can be seen at at corner entry with the current MGP when the exhaust spits out flames. I'dont know if every bike does it but I've seen pictures where the exhaust of the M1 seems to be on fire.
I think you are confused between an injected two stroke and a direct injected two stroke. With an injected two stroke all they did was replace the carb with a low presure injection system, while the DI engine injects into the combustion chamber.
The statement that expansion chambers become useless with DI is wrong. They can still be used. The only difference is that they only force air back into the cylinder instead of air and fuel.
Is there a future for the DI engine? I don't know
Aprilia has built a 600cc DI 2-stroke but it was cancelled and the rsv mille was produced instead. Aprilia was affraid nobody was intrested in a new 2 stroke.
Ktm will change there two stroke range to DI in the near future
The fact is that the DI 2-stroke is lighter, cheaper, smaller and more efficient than it's four stoke brother, but still has a bad reputation with the general public.
MOB
No I mean DI ........ it really is very old school ..... if you cared to look. As I said check out some of the beautiful old "hot bulb" engines. There were even older engines that were direct injected with things like sawdust or flour or charcoal dust ........ its as old as the hills
Chambers becoming useless is right. Show me one in use with DI
KTM are going electric anyway soon, so they will hang on to there existing two stroke range till then.
ANd on 4 strokes and overlap for non linearity of efficiency throughout the rev range ....... check out a thing called VVT ( variable valve timing )
The 750's never revved out smoothly and to anywhere near as high a revs. perhaps too much rotational mass ...... maybe there was a peak there too?
I've ridden a TZ750 and I'm sorry, but I have to disagree. Revving out wasn't a problem - stopping them before you completely exceeded the redline was
In reality it was a beast, especially when it got on the power, but off the power (where I mostly had it) it was like riding an RD350 - except for the noise, the ring-a-ding-a-ding and the very harsh exhaust note really got on your .... - especially with a helmet like a Bell Star... not exactly noted for their soundproofing. There was no power to speak of, about 20-25HP IIRC before you hit the power band, then it went form 25 to 90+ in about a second...
I rode a 'B' model RG500 as well, much more tractable and with about the same power, better handling and brakes and much lighter but nothing like riding something like a GSX1000 - I am fairly confident that the GSX or an R1 would piss all over the older GP two-strokes. but I fear that I am now too old to find out
Sorry, but you're wrong.
Aprilia has been making a DI 2T scooter for years - the DiTech - using Orbital Engine Co. injection system. Orbital have a few other customers as well (Piaggio, Peugeot and Kymco scooters, in outboard motors manufactured by Mercury and Tohatsu, and in personal watercraft manufactured by Bombardier).
And I am not sure where you get your info from, but injected 2T engines still use expansion chambers, it just isn't as critical to achieving efficient combustion. A DiTech scoot with a decent chamber kicks the arse of one without, just as if it were conventionally carbureted.
As to injected outboards, there's a ton of them. As with snowmobiles. Evinrude E-Tec is just one.
The biggest problem with injected two strokes is the cost - one of the main reasons to make two-strokes in the first place, but for boat motors, power/size/economy are big issues, price less so. If you can get power and fuel economy in a small package, boat owners will buy it.
With DI, emissions become a formality and power can stay the same while massively increasing MPG - 100MPG is pretty common on the DiTech. Or, you can go for power over economy and still retain some semblance of emissions control, like with the E-Tec. Evinrude have licenced the E-Tec injection system for some snowmobile manufacturers, notably Ski-Doo. Their 600 E-Tec is an alternative to their 1200cc 4T, with lighter weight, more power and better economy.
The Rotax-manufactured Ski-doo E-Tec:
KTM have one ready to race, should the regs allow it:
Joined Jun 2007
10K Posts | 1K+
Norah Head
I've ridden a TZ750 and I'm sorry, but I have to disagree. Revving out wasn't a problem - stopping them before you completely exceeded the redline wasThat and trying to keep the rear wheel behind the front and on the deck.
In reality it was a beast, especially when it got on the power, but off the power (where I mostly had it) it was like riding an RD350 - except for the noise, the ring-a-ding-a-ding and the very harsh exhaust note really got on your .... - especially with a helmet like a Bell Star... not exactly noted for their soundproofing. There was no power to speak of, about 20-25HP IIRC before you hit the power band, then it went form 25 to 90+ in about a second...
I rode a 'B' model RG500 as well, much more tractable and with about the same power, better handling and brakes and much lighter but nothing like riding something like a GSX1000 - I am fairly confident that the GSX or an R1 would piss all over the older GP two-strokes. but I fear that I am now too old to find out
I know you are saying you disagree but then you go on to say the same ......
When I say rev out smoothly I guess it could be said as tractability.
I am aware of the beastiness of the TZ ..... I even rode a dirt version ......... it was stupid
Also rode a somewhat worked 750 triple Kwaka ........ it was plain crazy.
I would have to say they had the torque over the 500 though when I think of it .... still they were nothing on modern bikes.
You bad `un,you`ve put me in a state of drool !!!
Joined Aug 2008
6K Posts | 748+
Thailand
.... Suter's 50,00 Euros... Try this for 15,000 Euro's TwoStrokeShop RS500
Or if ya got bigger balls... Big ... Two Strokes
BTW the RS500 comes in at about 1.9lbs per HP whereas the R1 is lagging back at 2.2lbs per HP... not bad for a forgotten (and according to some forum wankers) useless technology!!!
Or if ya got bigger balls... Big ... Two Strokes
BTW the RS500 comes in at about 1.9lbs per HP whereas the R1 is lagging back at 2.2lbs per HP... not bad for a forgotten (and according to some forum wankers) useless technology!!!
`kin hell,brilliant stuff ,Mick.
It's good to see that not everbody buys the 4-stroke PR.
183hp and 124kg
http://www.youtube.com/watch?v=jQoY7ECyoN8&NR=1&feature=fvwp
MOB
Hey MOB,I`ve been trying to follow the progress of the Tul-Aris since I mentioned it about a year ago on here. Fantastic machine,should`ve been in MotoGP as a prototype but sadly not to be.
